Optical system with main function for motor vehicle

ABSTRACT

An optical system for a motor vehicle, the optical system performing at least one main optical function and including in particular a diffusion screen, at least one light source of the LED type, each LED of the optical system producing a set of rays of light to be propagated in the diffusion screen wherein the screen is in the form of a curved sheet, with an upper lateral flange and a lower lateral flange which meet at a periphery which has in particular a rear face and a front edge and the principal function is performed essentially via an output face constituted by the front edge of the diffusion screen.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to French Application No. 0801168 filedMar. 3, 2008, which application is incorporated herein by reference andmade a part hereof.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The subject of the present invention is an optical system for a motorvehicle having a stylized main function, performed by means of at leastone light source, in particular of the light-emitting diode type. Theessential purpose of the invention is to propose, on the basis of alimited number of light sources, preferably LEDs, an optical systemperforming a main optical function by means of a transmission screen,the visible surface of which is sufficient to satisfy the regulatoryrequirements of the optical function under consideration. The termoptical system refers to an element forming part or all of a headlampdevice, exhibiting at least one light source and means of performing atleast one optical function; optical function refers to the production ofa regulatory light beam for the production of certain of the lightsmentioned below.

The domain of the invention is, in general, that of the lights or lampsof motor vehicles. In this domain, various types of lights are known,among which are included essentially:

-   -   tail lights, or position lights, of low intensity and range;    -   low beam lights, or dipped lights, of higher intensity and with        a range on the road in the vicinity of 70 meters;    -   long-range high-beam headlamps, and additional lights of the        long-range type, with a zone of vision on the road in the        vicinity of 200 meters;    -   advanced headlamps, known as dual-mode, which combine the        functions of dipped headlights and full beam headlights by        incorporating a detachable mask;    -   fog lamps;    -   signalling lights, in particular front and rear turn indicators,        reverse lights, or tail lights;    -   signalling devices of the position light type for daytime use,        known as DRL (Daytime Running Light) devices.

The domain of application of the invention is essentially that relatingto brake lights, turn indicators, position lights or DRL.

2. Description of the Related Art

For all of these headlamps and lights, the light sources traditionallyused are of the halogen lamp type, or discharge lamps. But for someyears now, automotive equipment suppliers have proposed the utilizationof light-emitting diodes, or LEDs; this utilization concerns, forexample, indicator lights or rear lights.

Light-emitting diodes present a certain number of advantages:

-   -   first of all, for a long time, it has been known that this type        of diode does not send out beams omnidirectionally, but radiates        in a half space opposite a substrate which supports the P-N        junction of the diode considered; thus, by using radiation more        directionally than halogen or discharge lamps, from the state of        the art, the quantity of energy wasted is less than with        discharge or halogen lamps;    -   further, these diodes have recently been improved in terms of        the intensity of radiated power. Moreover, manufactured diodes        have for a long time emitted radiation in red, but now also in        white, which expands the field of their potential uses. The        amount of heat which they give off is relatively limited, and a        certain number of constraints, in connection with the        dissipation of heat in state of the art headlamp devices, no        longer apply; the problem of heat dissipation, however, remains        important for power LEDs;    -   finally, diodes consume less energy than discharge or halogen        lamps, even at the same radiation intensity; they take up little        space, and their particular shape offers new possibilities for        the creation and the configuration of the complex surfaces        associated with them, in particular by arranging them on        electronic supports of the flexboard type.

The use of LEDs has become more and more widespread, in particular torespond to the aesthetic criteria desired by vehicle manufacturers. Thisuse especially enables the production of headlamps presenting originalvolumes, for example by arranging LEDs three-dimensionally, i.e. on anon-plane support substrate, within the headlamp devices in question, oragain, by using light guide type elements.

Furthermore, an optical system has recently been proposed in whichdifferent LEDs were specifically used to create a curtain of light bymeans of a screen inside the optical system, in which the light producedby the diode or diodes is propagated, the optical system also performingan optical function, known as the main optical function by comparisonwith any other optical function which may be performed by the opticalsystem in question, in the form of a light beam generated by a thirdlight source. In this optical system, it is necessary to make use of aplurality of light sources, as the LEDs used are not involved in theperformance of the main optical function. The cost of such an opticalsystem is therefore high, due to the large number of light sources itrequires, and, for the same reasons, it takes up a lot of space.

The term curtain of light refers to a surface illuminated by part of anoptical system, the illumination being produced by light beamscirculating inside a volume, in particular delimited by the illuminatedsurface, the illumination having until then a purely decorativefunction, not executing, or not contributing to—or onlyinsignificantly—the performance of the main optical function.Advantageously, the illumination produced is as continuous as possible,with no pixelization effect.

SUMMARY OF THE INVENTION

The object of the invention is to propose a solution to the problems anddisadvantages which have just been explained. In one aspect of theinvention, an optical system is proposed in which the number of lightsources involved is limited, preferably by limiting the utilization ofLEDs to the performance of a main function. Moreover, in another aspectof the invention, a screen is disposed in which are diffused thesignals, or beams, of light produced by the light sources, in particularLEDs, in such a way that, due to the positioning of the diffusionscreen, it is essentially an output edge of the screen which contributesto the performance of the desired main function; the visible illuminatedsurface is increased by the shape of the screen considered, a lateralflange of the screen diffusing light so as to contribute to theperformance of the desired main function. Advantageously, thepositioning of the diffusion screen is such that it contributes to theperformance of a second optical function of the lateral marking type,this function being known in English as a “side marker”.

The invention thus essentially concerns an optical system for a motorvehicle, the optical system performing at least one main opticalfunction and comprising in particular:

-   -   a diffusion screen, also known as a light guide;    -   at least one light source, notably of the LED type, each light        source of the optical system producing a set of rays of light        which are propagated in the diffusion screen.

In one aspect, the invention comprises a system in which:

-   -   the screen is in the form of a sheet, notably curved or        substantially plane, with an upper lateral flange and a lower        lateral flange which are joined by means of a periphery having a        rear face, a front edge, the periphery can also comprise a first        lateral face and a second lateral face;    -   the main function is performed essentially via an output face        constituted by the front edge of the diffusion screen; and    -   at least one part of the upper lateral flange diffuses a light        beam contributing notably to the performance of the main        function and/or performing a complementary optical function.

The optical system according to the invention may comprise, in additionto the main characteristics which have just been mentioned in thepreceding paragraph, one or more supplementary characteristics includingthe following:

-   -   the front edge has a thickness of between 3 and 5 millimeters,        notably 4 millimeters;    -   a first part of the upper lateral flange diffuses a light beam        contributing to the performance of the main function;    -   at least one part of the upper lateral flange diffuses a light        beam and is oriented in such a way as to increase the visible        illuminated surface of the optical system in the direction of        emission of the main function;    -   the main optical function performed is of the brake light type,        or of the position light type, or of the turn indicator type;    -   a second part of the upper lateral flange diffuses a light beam        performing a complementary optical function;    -   the complementary optical function performed is of the lateral        marking type;    -   the upper lateral flange diffuses a light beam via a plurality        of micro-roughnesses suitable to disperse to the exterior of the        diffusion screen some of the rays of light propagating in the        diffusion screen, these micro-roughnesses forming notably a        plurality (110) of minidiscs;    -   the micro-roughnesses form minidiscs having a diameter        substantially between two tenths of a millimeter and six tenths        of a millimeter, typically four tenths of a millimeter;    -   the light sources, in particular LEDs, are arranged opposite the        rear face of the diffusion screen;    -   it comprises at least one lateral face, the light sources, in        particular the LEDs, being arranged opposite at least one of the        lateral faces of the diffusion screen;    -   the light sources, in particular LEDs, are arranged opposite a        single lateral face of the diffusion screen;    -   the rear face of the periphery comprises a plurality of        reflecting prisms suitable to direct the light beams produced by        the light sources, in particular LEDs, to the front edge of the        diffusion screen.

The supplementary characteristics are associated, according to allpossible combinations and to the extent that these supplementarycharacteristics are not mutually exclusive, in different embodiments ofthe subject matter of the invention.

The present invention also relates to a headlamp or to a signallinglight for a motor vehicle equipped with an optical system according tothe invention, with its main characteristics, and possibly one or moresupplementary characteristics which have just been mentioned.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

The invention and its different applications will be better understoodby reading the following description and examining the accompanyingfigures.

These figures are shown only by way of indication and do not in any waylimit the invention. The figures show:

FIGS. 1A, 1B and 1C are different perspectival views of a firstembodiment of an optical system according to the invention;

FIG. 2 is a perspective view of a second embodiment of an optical systemaccording to the invention;

FIG. 3 is a perspective view of a third embodiment of an optical systemaccording to the invention;

FIG. 4 is a top view of the third embodiment shown in FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The different elements appearing in several figures, unless otherwisestated, have retained the same reference numbers.

FIGS. 1A, 1B and 1C show a first embodiment of an optical systemaccording to the invention in, respectively, a first position, a secondposition and a third position. A three-dimensional orthogonal marker isshown in these figures, with an axis of abscissas X corresponding to theaxis of displacement of the reversing vehicle, and a normal Z axiscorresponding to the vertical.

In these figures, the optical system 100 according to the inventionconsists of a diffusion screen 113 and of a plurality of LEDs 101producing the rays of light 102 which are intended to be propagated inthe diffusion screen 113. The screen 113 is made from a transparentplastic material, in particular of the type PMMA (for PolyMethylMethAcrylate) or PC (for superfluid high transmission PolyCarbonate).

Advantageously, the LEDs 101 is all arranged on a single planesubstrate, not shown, which holds them in position and controls them.

The diffusion screen 113 takes the form of a curved sheet. A term ofthis type refers to the fact that the screen 113, if it were flattened,would constitute an element of homogeneous thickness, of approximatelyfour millimeters, said thickness being small in size in relation to theother dimensions of the flattened shape; which is of the quadrilateraltype in the example shown.

The diffusion screen 113 is thus characterized by an upper lateralflange 108, a lower lateral flange 109, these two parts being linked bya periphery 103, having a front edge—i.e. a linear face—104, a firstlateral face 105, a second lateral face 106 and a rear face 107. Thefront edge 104 is the face of the optical system which is directlyvisible to an observer positioned at the rear of the vehicle equippedwith the optical system considered. In the examples shown, the diffusionscreen is curved such that an observer positioned at the rear of thevehicle sees at least part of the upper lateral flange 108. Such acharacteristic is expressed by the fact that at least one of the lateralfaces 105 or 106 of the periphery 103 constitutes a curved, or at leastinclined, segment.

In the first example shown, the diodes 101 are arranged opposite therear face 107, at the level of which the rays of light 102 which theyproduce enter the diffusion screen 113. The rays of light 102 are thuspropagated in the volume defined by the diffusion screen 113, possiblyafter reflection from the lateral faces 105 and 106, to exit from thediffusion screen 113 at the front edge 104 in the form of a light beam111, where a main optical function is at least partially performed, forexample of the sidelight type.

Advantageously, the upper lateral flange 108 consists of a plurality ofminidiscs with a diameter of between 2 and 6 tenths of a millimeter,which make it possible, with the aid of the micro-roughnesses which theyexhibit, to diffuse to the exterior of the diffusion screen 113, througha first part 115 of the upper lateral flange 108, some of the rays oflight 102 in the form of a light beam 112. The term micro-optic surfaceis often used to describe such a diffusion surface. In FIG. 1B, theminidiscs are represented by points inside a zone 110 surrounded by acircle, shown enlarged at the top right of the illustration of thediffusion screen 113. In the enlarged illustration, a light beam 112generated by one of the minidiscs has been represented by a set ofarrows. Obviously, most if not all of the minidiscs generate a lightbeam 112. Two other zones 110 have been shown in diagram form on thediffusion screen 113. The minidiscs may preferably be distributed overthe entire lateral flange 108. The light beams 112, corresponding to thelight diffused by the minidiscs, contribute to the performance of themain optical function by increasing the visible illuminated surface ofthe optical system 100. The visible illuminated surface may thus be madelarger to a greater or lesser degree by inclining the optical system 100more or less.

The front edge 104 is rendered homogeneous with the aid of a surfacewhich is either perfectly diffusing to conceal the hot points and todistribute the beams spatially, or covered in optical patterns(equivalent to pseudo-toric surfaces of small dimensions to match thesurface) to distribute the beams spatially, or perfectly polished toreveal the hot points corresponding to the position of the origin of theemitters, the LEDs.

Advantageously, part 114 of the upper lateral flange 108 is used toperform a complementary function of the lateral marking type (sidemarker in English): to this end, provision is made that the part 114 issubstantially vertical, and that it projects at least partially beyondthe body of the vehicle so as to be visible when the vehicle is viewedfrom the side.

FIG. 2 shows a second embodiment 200 of an optical system according tothe invention. The second embodiment differs from the first embodimentby the following characteristics:

-   -   the LEDs 201, producing light beams 202, are arranged opposite        the first lateral face 105, and not opposite the rear face 107;    -   the rear face 107, which was plane in the first embodiment 100,        has been replaced by a rear face 207, consisting of a succession        of reflecting prisms 208, which use total reflection to redirect        the light beams 202 to the front edge 104, over the entire        length necessary to the performance of the main function, as in        the first embodiment described.

The other elements which appeared in the first embodiment are stillpresent, and fulfill the same function.

FIGS. 3 and 4 show a third embodiment 300 of an optical system accordingto the invention. It differs from the first embodiment in that thediffusion screen 313 is substantially plane, thus in the form of asubstantially plane sheet. The lower 309 and upper 308 lateral flangesare substantially plane. Preferably, the rear edge 307 and the lateraledges 305 and 306 are also substantially plane. The output face 304preferably forms, with the upper lateral flange 308, an angle of over 90degrees and the diffusion screen 313 is oriented such that:

-   -   the output face 304 is substantially perpendicular to the        X-axis, this X-axis corresponding to the direction of emission        of the light of the main function; and    -   the upper lateral flange forms an acute angle in relation to the        transverse Y-axis, the front edge 304 and the lateral flange 308        are directly visible to an observer positioned facing the        direction of the X-axis.

In this third embodiment, the orientation thus makes it possible firstlyto have part of the main function essentially or mainly performed by theoutput edge 304 according to the X-axis, i.e. towards the rear of thevehicle when the device is situated in a rear light of the vehicle, andsecondly, by means of the light diffused by the upper lateral flange308, to have an increase in the visible surface according to the X-axisof this main function, and a repeat function along the Y-axis, that is,on the side of the vehicle when the device is situated at the rear ofthe vehicle.

The other elements, for example the micro-roughnesses which appeared inthe first embodiment, are still present in this third embodiment andfulfill the same function.

To explain the present invention, the expression “upper lateral flange”generally refers to the lateral flange which is oriented towards theexterior of the vehicle and thus visible to an observer. In particular,it could be applied to a diffusion screen which, once mounted on thevehicle, would show a visible lateral flange which is vertical, or eveninclined towards the ground.

While the forms of apparatus herein described constitutes preferredembodiments of this invention, it is to be understood that the inventionis not limited to these precise forms of apparatus, and that changes maybe made therein without departing from the scope of the invention whichis defined in the appended claims.

1. An optical system for a motor vehicle, said optical system performingat least one main optical function particular comprising: a diffusionscreen; at least one light source, of an LED type, each of said at leastone light source of the optical system producing a set of rays of lightto be propagated in the diffusion screen; wherein said diffusion screenis in the form of a sheet with an upper lateral flange surface and alower lateral flange surface which are joined by a periphery having arear face and a front edge, wherein the diffusion screen is curved witha rear facing portion and a side facing portion; wherein said opticalsystem performs both a main optical function and a complementary opticalfunction said at least one main optical function is performedessentially via diffusively illuminating the rear facing portion of theupper lateral flange and an output face constituted by the front edge ofthe diffusion screen wherein the rear facing portion and front edge arevisible from a rear of the vehicle; and wherein said complementaryoptical function is performed essentially via the side facing portion ofthe upper lateral flange that is visible from a side of the vehicle,wherein said at least one main optical function provides a brake,position light, or turn indicator on a rear of the motor vehicle, andsaid complementary optical function provides a light on a side of themotor vehicle and provides a different optical function than said atleast one main optical function.
 2. The optical system according toclaim 1, wherein the front edge has a thickness of between 3 and 5millimeters.
 3. The optical system according to claim 1, wherein at oneleast part of said upper lateral flange diffuses a light beam and isoriented in such a way as to increase the visible illuminated surface ofthe optical system in the direction of emission of said at least onemain optical function.
 4. The optical system according to claim 1,wherein said upper lateral flange surface diffuses a light beam whichperforms said complementary optical function type wherein saidcomplementary optical function propagates rays through at least one ofsaid lower lateral flange or upper lateral flange thereby causing lightrays to be propagated laterally with respect to an axis of saiddiffusion screen to provide a side marker light on said side of themotor vehicle.
 5. The optical system according to claim 1, wherein saidupper lateral flange diffuses a light beam via a plurality ofmicro-roughnesses suitable to disperse to the exterior of the diffusionscreen some of said rays of light to be propagated in said diffusionscreen, said plurality of micro-roughnesses forming notably a pluralityof minidiscs.
 6. An optical system for a motor vehicle, said opticalsystem performing at least one main optical function and comprising; adiffusion screen; at least one light source, notably of an LED type,each of said at least one light source of the optical system producing aset of rays of light to be propagated in the diffusion screen; whereinsaid diffusion screen is in the form of a sheet, curved or substantiallyplanar, with an upper lateral flange and a lower lateral flange whichare joined by a periphery having a rear face and a front edge; said atleast one main optical function is performed via an output faceconstituted by the front edge of the diffusion screen; and at least onepart of said upper lateral flange diffuses a light beam that contributesto a performance of at least one of said at least one main opticalfunction or a complementary optical function; wherein said upper lateralflange diffuses a light beam via a plurality of micro-roughnessessuitable to disperse to the exterior of the diffusion screen some ofsaid rays of light to be propagated in said diffusion screen, saidplurality of micro-roughnesses forming notably a plurality of minidiscs;wherein said plurality of micro-roughnesses form minidiscs with adiameter of between two tenths of a millimeter and six tenths of amillimeter, typically four tenths of a millimeter.
 7. The optical systemaccording to claim 1, wherein said at least one light source is arrangedopposite the rear face of the diffusion screen.
 8. A headlamp or signallamp for a motor vehicle, wherein said headlamp or signal lamp is fittedwith the optical system according to claim
 1. 9. The optical systemaccording to claim 2, wherein at one least part of said upper lateralflange diffuses a light beam and is oriented in such a way as toincrease the visible illuminated surface of the optical system in thedirection of emission of said at least one main optical function. 10.The optical system according to claim 2, wherein said upper lateralflange diffuses a light beam which performs said complementary opticalfunction wherein said complementary optical function is of a lateralmarking type.
 11. The optical system according to claim 2, wherein saidupper lateral flange diffuses a light beam via a plurality ofmicro-roughnesses suitable to disperse to the exterior of the diffusionscreen some of said rays of light to be propagated in said diffusionscreen, said plurality of micro-roughnesses forming notably a pluralityof minidiscs.
 12. The optical system according to claim 3, wherein saidupper lateral flange diffuses a light beam via a plurality ofmicro-roughnesses suitable to disperse to the exterior of the diffusionscreen some of said rays of light to be propagated in said diffusionscreen, said plurality of micro-roughnesses forming notably a pluralityof minidiscs.
 13. The optical system according to claim 3, wherein saidat least one light source is arranged opposite the rear face of thediffusion screen.
 14. The optical system according to claim 3, whereinsaid optical system includes at least one lateral face, said at leastone light source being arranged opposite said at least one lateral faceof the diffusion screen.
 15. The optical system according to claim 2,wherein said thickness is 4 millimeters.